 # GRAVITY AND MOTION. Bellringer #11 1.While approaching a red light a semi truck takes longer and uses more force on the breaks to stop than a small car.

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GRAVITY AND MOTION

Bellringer #11 1.While approaching a red light a semi truck takes longer and uses more force on the breaks to stop than a small car does. Which of the following gives reasoning for this situation? a. The truck is going too fast. b. The truck has more inertia c. The truck has more momentum due to its’ mass. d. BOTH B and C 2.While riding the bus to school this morning your bus driver took a sharp left hand turn. Which direction will your body go? a. Toward the left b. Toward the right c. Toward the back d. Toward the front 3.Which of Newton’s 3 laws best explains your reasoning for question 2? a. Newton’s 1 st law. b. Newton’s 2 nd law. c. Newton’s 3 rd law

Bellringer #13 1.A penny resting on your elbow wants to remain at rest until an outside force acts on it. This statement proves that the pennies: a. Are lazy b. Have gravity acting on them c. Have inertia 2.A bowling ball and a ping pong ball are rolling across the floor. You notice that the bowling ball is much harder to stop than the ping pong ball. This is because: a. The bowling ball has more momentum b. The ping pong ball has more momentum c. The bowling ball is bigger 3.The pop can engine had six holes around the bottom to let water flow out. What would make the pop can engine move faster according to Newton’s second law of motion? a. Less holes in the bottom b. More holes in the bottom c. The temperature of the water

Question???? Which object will land sooner if dropped at the same time, a ping pong ball or a golf ball ?

Acceleration Due To Gravity Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects. The mass of an object does not affect the rate at which it falls.

ACCELERATING AT A CONSTANT RATE All objects accelerate toward Earth at a rate of 9.8 m/s/s. WHAT DOES THIS MEAN? This means that for every second an object falls, the object’s downward velocity increases by 9.8 m/s.

DOES AIR RESISTANCE AFFECT FALLING OBJECTS? Yes!! THE FORCE OF GRAVITY PULLS OBJECTS DOWNWARD AS THE FORCE OF AIR RESISTANCE PUSHES IT UPWARD. FREE FALL- when an object is being pulled down by gravity, but no other forces are acting on it. Does free fall occur with air resistance?

NEWTON’S FIRST LAW OF MOTION AKA: LAW OF INERTIA An object at rest remains at rest and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force. Inertia is the tendency of all objects to resist any change in motion. A golf ball on a tee. The man will remain in motion until a force stops his movement. Examples:

NEWTON’S SECOND LAW OF MOTION The acceleration of an object depends on the mass of the object and amount of force applied. FORCE=MASS X ACCELERATION Or a=F/m How does Newton’s Second Law explain why the shuttle’s acceleration increases during takeoff?

NEWTON’S THIRD LAW OF MOTION For every action there is an equal and opposite reaction. FORCES ALWAYS ACT IN PAIRS. The action force is the swimmer’s hand and feet pushing the water. The reaction force is the water pushing on the swimmer’s hands and feet.

MORE EXAMPLES OF ACTION AND REACTION FORCE PAIRS The rabbit’s legs exert a force on Earth. Earth exerts an equal force on the rabbit’s legs, causing the rabbit to accelerate upward. The shuttle’s thrusters push the exhaust gases downward as the gases push the shuttle upward with an equal force.

WHAT IS MOMENTUM? MOMENTUM is a property of a moving object that depends on the object’s mass and velocity. THE MORE MOMENTUM AN OBJECT HAS, THE HARDER IT IS TO STOP THE OBJECT OR CHANGE ITS DIRECTION. Momentum=mass x velocity

LET’S PRACTICE

Explain Newton’s First Law of Motion using this picture. A plane will not soar in the air unless it is pushed by the exhaust from its jet engines.

Newton’s Second Law of Motion - Which would you have to apply a greater force to stop and go? - Which would you rather buy gas for? -Which would you rather be driving in a head-on collision?

NEWTON’S THIRD LAW OF MOTION LIST and DESCRIBE the action and reaction forces in the following picture.

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